| 摘要 |
<p>A novel polyhydroxy oligomer crosslinkable with polyisocyanate to form a coating composition adapted for use as an automotive topcoat which upon curing forms a hard, glossy, durable coating with outstanding weatherability and excellent resistance to solvents and water. The coating composition comprises: (A) a polyhydroxy oligomer having a number average (?n) molecular weight of between about 300 - 2000 and being the reaction product of: (i)an acid ester made by reacting: (a) a C3 - C10 aliphatic branched diol, and (b) an alkyl hexahydrophthalic anhydride, wherein (a) and (b) are combined in the reaction mixture in amounts sufficient to result in reaction in a molar ratio of greater than 1:1 up to 1:2; and (ii) a monoepoxide C2 - C10 monomer, the monomer is included in an amount sufficient to provide reaction of about 1.0 epoxide groups for each acid group of the acid ester; (B) a polyisocyanate crosslinking agent; and (C) optionally a hydroxy functional additive. The polyisocyanate crosslinking agent is included in the composition in an amount sufficient to provide between about 0.50 preferably between about .8 and 1.3 reactive isocyanate groups per hydroxyl group included in the composition either on the polyhydroxy oligomer or as a hydroxyl group of the hydroxy functional additive.</p> |
